1. Field of the Invention
This invention relates to an image sensor for a facsimile machine, an optical character reader or the like.
2. Description of the Related Art
FIG. 1 of the accompanying drawings is a fragmentary cross-sectional view, taken along a plane perpendicular to the direction of scanning, of a typical conventional image sensor. In this image sensor, a transparent cover (glass cover) 2 is mounted on the top of a frame 1, and there are mounted in the frame a first substrate 4 with a light emitting element 3 for radiating light over an original W as an objective engageable with the glass cover 2, a rod lens array 5 as an optical system for condensing light reflected from the original W, and a second substrate 7 with a light receptor 6 for receiving the light through the rod lens array 5.
With this conventional image sensor, light from the light emitting element 3 is radiated over the original W, which is brought into contact with the glass cover 2 by a platen roller (not shown), at an angle of about 45.degree. with respect to the plane of the glass cover 2. The light reflected by the original W perpendicularly to the plane of the glass cover 2 is condensed by the rod lens array 5 and is then received by the light receptor 6 which is situated directly under the rod lens array 5 where the resulting light is converted into electrical signals.
In the conventional image sensor, in order to detect the light reflected from the original W, there are mounted on the second substrate 7 a package of electronic elements (not shown) such as resistors and capacitors in addition to the light receptor 6. These electronic elements are usually connected respectively to their associated pads on the second substrate 7 by soldering.
However, as many soldering operations as there are electronic element terminals are needed, which would take a very long time and hence would increase the cost of production. The more terminals there are to be soldered, the greater the amount of soldering flux, which is widely used in soldering, will become so that the electronic elements can be easily :affected. More particularly, if soldering flux flies to the light receptor, the light receptor would be deteriorated to cause the image sensor to malfunction. To avoid this problem, in the conventional art, terminals are connected by using silver paste, which would increase the cost of production. To prevent flux from flying to the light receptor, in the image sensor disclosed in Japanese Patent Laid-Open Publication No. HEI 1-289279, electronic elements are soldered to the substrate at one surface other than that where the light receptor is mounted. Yet this method is disadvantageous in that a preheater block cannot be brought into contact with the rear surface of the substrate and that it is impossible to reduce time taken to solder.